Effect of copper doping on structural, optical and electrical properties of Cd 0·8 Zn 0·2 S films prepared by chemical bath deposition

Cd 0·8 Zn 0·2 S:Cu films of 1 ·3–6 ·1 mole percentage of copper have been grown on mica substrate by using chemical bath deposition technique. The films have been characterized by using XRD, SEM and UV spectrophotometer. X-ray diffraction studies have shown that the films are polycrystalline. The average crystallite size as measured from XRD data is in the range of 125–130 nm. The activation energies of Cd 0·8 Zn 0·2 S:Cu films, as observed from d.c. conductivity studies in the temperature range (77–300 K) studied, decreased with the increase in Cu concentration. The optical absorption studies have revealed that the energy gap increases gradually with an increase in Cu concentration, whereas conductivity studies have shown an anomalous increase in conductivity in films of 3 ·8 mole percentage of Cu. SEM pictures have revealed the presence of defects with spherical structure having fibre network. The variation of electrical conductivity is explained based on the defects present and by adopting tunneling mechanism.